Sensitizers are one of the most crucial components for the preparation of DSSCs because they affect not only the incident photon conversion efficiency (IPCE) of the cells but also the stability of the components.
Thus far, various sensitizers have been proposed by scientists in hopes of increasing the efficiency of DSSCs and prolonging their service life. For example, Michael Grätzel, a Swiss scientist, developed in 1999 a sensitizer named N719, which was widely used in the industry for its high IPCE.
However, because N719 cannot sustain high temperature and falls off easily after being used for a period of time, solar cells containing the same usually can no longer work normally after three years of usage.
In order to improve the stability of N719 under the existence of a heat source or in a moist condition, Grätzel further proposed in 2003 another sensitizer named Z907. Proved by experiments, Z907 can still possess 94% of its original efficiency after being operated continuously for 1,000 hours under 80° C. In contrast, the efficiency of N719 decreases 35% under the same condition.
Although Z907 demonstrates great sustainability in long-term stability testing, Z907 is not completely satisfactory because it has a molar absorption coefficient lower than N719.
Accordingly, it is highly desirable for scientists to develop novel sensitizers with high IPCE and thermal stability.